When a narrow channel or two river collided and merged, will increase the speed of the water, stronger. Water flow and flow are similar in many ways, it inspired a batch from southern nanyang technological university in Singapore and researchers at the university of Nebraska Lincoln to investigate whether the flow of light in a waveguide in showed the same characteristic, waveguide can be used for electromagnetic waves transmitted between the endpoints of a linear structure.

According to the report in the journal of applied physics letters, their research by the infrared sensing characteristics of fiber optic micro couplers for testing, and has set up a sensor, the sensitivity than conventional biochemical sensors based on optical fiber high sensitivity 20 times.

By using a technical method to increase the optical fiber to the surrounding environment of the small, the sensitivity of the change of the refractive index of optical fiber on the concentration of small molecule on or near the surface of the fiber change can be detected. Although the general idea is well known, the special method to solve the problem, the sensitivity of an existing.

The team of optical fiber coupler sensor is the basic concept of "interference of light, will be transmitted along the fiber coupler," Lei Wei explained that he is the nanyang technological university institute of electrical and electronic engineering and assistant professor of college of engineering.

Interference is a common natural phenomena, as light, sound, and even water waves in the same space, will likely.

"In our work, when light travels along the fiber, two different optical fiber transmission mode in the coupler can be inspired, and interference will occur," Wei said.

Sensors based on optical interference has been used in many applications, including biological measure field and using optical fiber to make these devices are very compact and the economy.

"But it is reported that at present most of the fiber optic biosensor is a weakness, they showed a high sensitivity only when the surrounding refractive index (RI) and the refractive index of the fiber will happen when (1.44) is very close," wei said. "In practice, detect biological molecules is actually the preparation of aqueous solution in the form of a RI fairly close to the water of the refractive index (1.33), therefore, achieve high sensitivity of the track analysis and small molecular detection is fundamentally based on optical fiber sensor is challenging.

The team's research process, they created a kind of optical fiber coupler can achieve high sensitivity of the sensor "low refractive index sensing range, in 1.33 refractive index range, through the accurate design parameters, minimizing" accidentally supermodel "and" supermodel 'group refractive index difference, "he added.

What is called a supermodel? A typical optical fiber coupler is composed of two parallel, closely arranged two input micro fiber (P1 and P2) and two outputs (P3 and P4) port, two transition cone, and the central unified "waist" area. Produced by the input mode of injection mode field is known as "supermodel", including the distribution of the odd and even number. When the odd-even supermodel propagation along the fiber coupler, the exchange of power and the resulting interference spectrum can be obtained on the output side.

The group of the experimental results show that the sensor is more sensitive to 20 x than conventional fiber optic biosensor.

"The resulting ultrasensitive mechanism not only created a wide range of applications in the field of chemical and biological sensing opportunity, also widened the other repertoire of interferometric fiber optic sensor, even acoustic sensors," wei said.

Due to its high sensitivity, the team that is the ideal target analysis and the choice of small molecule detection.

"It can also be implemented in the field of medical diagnostics and environmental monitoring a variety of applications, such as the early detection of cancer and other disease, as well as the detection of heavy metals in the water," Wei said. "In the near future, we hope to develop into a new sensing platform, has a high sensitivity and fast response time, and has the characteristics of feasibility, low cost, which can realize in the application of the doctor's office."

The team's next step is to "make the sensor array, and further discusses its sensing properties of cancer biomarkers," Wei said.